Bacterial composition,method and installation for the pre-treating effluents loaded with organic fatty substances

ABSTRACT

A bacterial composition, a process and a facility for the pre-treatment of effluent rich in organic fats of animal or vegetable origin. The bacterial composition principally is the bacterial strain  Klebsiella oxytoca . The process consists of supplying a homogenisation and/or processing vessel ( 1 ) with effluent to be pre-treated, as it is produced, activating a recirculation circuit ( 2 ) between the vessel and a biological reactor ( 3 ) to obtain a fat dilution rate situated between 0.400 h −1  and 1.500 h −1  for an initial fat concentration of 1 g/l, degrading the fats in the biological reactor ( 3 ) using the bacterial composition and discharging the pre-treated effluent to a final treatment unit such as a purification plant.

DESCRIPTION

[0001] The present invention relates to the field of the treatment ofeffluent rich in organic fats of animal or vegetable origin such asresult from industrial processes, particularly those implemented in thefood and agro-food field or in similar sectors. The invention relatesmost particularly to the field of the pre-treatment of said effluent andconcerns a bacterial composition, a process and a facility forpre-treating the above-mentioned effluent.

[0002] The treatment of the residual fats or lipids produced in industryposes a fair number of problems. Indeed, following the health problemsencountered in the treatment of animal fats (the so-called “mad cow”disease) and the new policies on environmental matters, requirements inconnection with treatments of this type of waste have become ever morerestrictive, both technically (bringing treatment a facility up tostandard, improving output, etc.) and in terms of cost.

[0003] In addition, existing treatment capacities, for example atcommunal purification plants, are often inadequate, particularly whenthe level of fats present in the effluent to be treated is high.

[0004] To try to resolve the problems connected with the treatment offatty effluent produced in large quantities, various solutions havealready been considered and some have been implemented.

[0005] Thus, it has been proposed in particular to spread said effluentdirectly over large areas of agricultural land and in this waydistribute the impact of dumping them on the environment, so as toachieve acceptable levels of surface pollution.

[0006] Another solution consists of storing said fats, possibly afterconcentration and/or special processing in an approved dumping facilitywith a view to final treatment in a specialised centre or incinerationunit.

[0007] Another route followed is composting the fats.

[0008] However, faced with the ever-increasing quantities of fattyeffluent produced, these solutions cannot be satisfactory in the medium-or long-term, particularly in view of the strengthening of presentanti-pollution regulations which mean or will mean that these processesdo not comply and/or are not economically viable.

[0009] Proposals have also been made to adapt conventional purificationplants by incorporating fat separators (static separators or with airinjection) or saponification techniques for the special treatment ofthis type of effluent.

[0010] However, this adaptation would cause costly over-sizing of saidplants to allow them to respond to the quantities of pollutantsgenerated, without however providing reliable control of changes in thelevel of pollution, and therefore of the quality of the final effluentdischarged, mainly due to the continuous operation of theseinstallations.

[0011] Finally, several processes for the biological treatment of fatsare known in which the effluents to be treated are put in contact withspecial bio-additives and/or a suitable purifying biomass that degradesthe fats by transforming them into gas and sludge. These processes canbe implemented aerobically or anaerobically.

[0012] However, the lactic acid bacteria employed in the processes usedat present do not allow complete hydrolysis of long-chain fatty acids,and this causes a damaging overload of organic matter in the aerationtank.

[0013] Moreover, the bacteria used at present do not retain, as theymultiply, the properties initially conferred on them when they werecreated by genetic manipulation. Frequent and costly inputs of newbacteria are therefore necessary to maintain the effectiveness of theprocess.

[0014] Consequently, the problem posed for the present inventionconsists of reducing the above-mentioned drawbacks and designing abacterial composition, a process and a facility for the pre-treatment ofeffluent rich in fats, more especially effluent from the food andagro-food field, that provide a more effective solution (output in termsof fats eliminated of over 90%), that are inexpensive and more reliableover time, and that allow the strictest regulatory requirements withregard to the purified effluent discharged to be met.

[0015] To this end, the present invention relates to a bacterialcomposition for the degradation of organic fats, characterised in thatit comprises principally the bacterial strain Klebsiella oxytoca, andthe use of a bacterial composition according to the present inventionfor the treatment or pre-treatment of effluent rich in organic fats,particularly effluent from the food or agro-food industry.

[0016] The present invention also relates to a process for thepre-treatment of effluent rich in organic fats, particularly effluentfrom the food and agro-food industry, characterised in that it consistsof directly pre-treating said effluent containing said fats when itleaves the place of production and in that it consists of accomplishingthe following stages:

[0017] supplying a homogenisation and/or processing vessel with effluentto be pre-treated, as it is produced and activating a recirculationcircuit between this vessel and a biological reactor so as to obtain insaid biological reactor a rate of fat dilution inversely proportional tothe fat concentration initially present in the effluent to bepre-treated, situated between 0.400 h⁻¹ and 1.500 h⁻¹ for a fatconcentration contained in said effluent to be pre-treated entering thehomogenisation and/or processing vessel of 1 g/l,

[0018] degrading said fats in said biological reactor using a bacterialcomposition according to the present invention, and

[0019] discharging the pre-treated effluent, now containing practicallyno fats, to a final treatment unit such as a purification plant.

[0020] Finally, the present invention also relates to a facility for thepre-treatment of effluent rich in organic fats, notably for theimplementation of the process according to the present invention,characterised in that it consists principally of at least onehomogenisation and/or processing vessel, at least one biological reactorof a capacity suited to the daily output of effluent to be pre-treatedand the fat concentration in that effluent, said biological reactorbeing connected to the homogenisation and processing vessel(s) by arecirculation circuit, at least one device for the controlled supply ofoxygen arranged in the biological reactor(s) and at least one means ofdischarging the pre-treated effluent, for example by overflow, outsidesaid biological reactor(s).

[0021] The invention will be better understood by referring to thedescription below, which relates to a preferred embodiment, given as anon-limiting example, and explained with reference to the accompanyingdiagrammatic drawings, in which:

[0022]FIG. 1 is a simplified diagrammatic outline of the processaccording to the invention, and

[0023]FIG. 2 is a simplified view from above of a facility according tothe present invention.

[0024] In accordance with the present invention, the bacterialcomposition for degrading organic fats is characterised in that itcomprises principally the bacterial strain Klebsiella oxytoca. It hasunexpectedly and surprisingly been found that the selected strain isparticularly effective in the degradation of organic fats, in particularin the degradation of fats of animal or vegetable origin from the foodor agro-food industry.

[0025] Some non-limiting examples of fats that can be treated bybacteria according to the present invention are fats from pork butchers,butchers, caterers, restaurants, communal catering facilities, animalquartering companies, abattoirs, etc.

[0026] According to a first embodiment, the bacterial compositionaccording to the present invention is characterised in that it alsocomprises the bacterial strain Serratia odorifera and/or Aeromonashydrophyla.

[0027] Surprisingly and unexpectedly, the specific association of thesebacterial strains proved to be particularly effective and economic inthe degradation of the aforementioned fats. The strains according to theinvention therefore provide excellent output in terms of degraded fats.

[0028] In practice, the micro-organism(s) according to the invention areadvantageously added in a solid lyophilised form into the culture mediumcontained in the fat treatment reactor.

[0029] As an indication, the average bacterial quantity contained in thecomposition according to the present invention is of the order of 10¹⁶bacteria/g of solid matter. When the micro-organisms are seeded, anaverage quantity of 2.10¹⁵ bacteria/m³ is necessary for the propereffectiveness of said micro-organisms.

[0030] Growth conditions for the strains Klebsiella oxytoca, Serratiaodorifera and Aeromonas hydrophyla have also been studied. Unexpectedlyand surprisingly, it was noted that the aforementioned strains developparticularly well in aerobic conditions, in a wide range of temperaturessituated preferably between 15° C. and 40° C., and for a huge range ofpH encompassing both slightly acid (pH=5) and slightly alkaline (pH=9)environments, and this permits easier and more effective use of thecultures in question. The very robust nature of these bacteria alsoguarantees good development and optimal longevity, and therefore highand stable performance over time.

[0031] Preferably, the bacterial composition according to the presentinvention is characterised in that it is composed of:

[0032] 60% to 90%, preferably about 80% by weight of bacteria of thestrain Klebsiella oxytoca,

[0033] 5% to 20%, preferably about 10% by weight of bacteria of thestrain Serratia odorifera, and

[0034] 5% to 20%, preferably about 10% by weight of bacteria of thestrain Aeromonas hydrophyla, the total of the three strains being equalto 100%.

[0035] In this way, a mixture of bacteria is obtained that is not onlyvery effective in terms of fat degradation (cf. table below) but alsohas practical implementation advantages, such as, for example, reducedcosts, good longevity, easy conditions for culture, elimination,recycling, etc.

[0036] The aforementioned bacterial strains initialise fat degradationby cutting the ester bond between the glycerol and long fatty acidchains since they contain lipases that allow this enzymatic cutting tooperate. Degradation (□-oxidation) of the fatty acids follows based onthe free carboxyl group by decarbonation of an acyl group. This finalstage is also accomplished by these strains.

[0037] Thus, the bacterial composition according to the presentinvention can be used for the treatment or pre-treatment of effluentrich in organic fats, particularly effluent from the food or agro-foodindustry.

[0038] Reference will now be made to FIG. 1 which illustratesdiagrammatically the process of the present invention. Said process ischaracterised in that it consists of pre-treating directly said effluentcontaining said fats as it leaves the place of production and in that itconsists of accomplishing the following stages:

[0039] supplying a homogenisation and/or processing vessel 1 witheffluent to be pre-treated, as it is produced and activating arecirculation circuit 2 between this vessel and a biological reactor 3so as to obtain in said biological reactor 3 a rate of fat dilutioninversely proportional to the fat concentration initially present in theeffluent to be pre-treated, situated between 0.400 h⁻¹ and 1.500 h⁻¹ fora concentration of fats contained in said effluent to be pre-treatedentering the homogenisation and/or processing vessel 1 of 1 g/l,

[0040] degrading said fats in said biological reactor 3 using abacterial composition according to the present invention, and

[0041] discharging the pre-treated effluent, now containing practicallyno fats, to a final treatment unit such as a purification plant.

[0042] The process according to the present invention allows work to bedone directly on the flow of fat-rich effluent, in other words with noprior physico-chemical separation. Of course, it is also possible towork on fats that have undergone prior physical treatment.

[0043] Degradation of fats by hydrolysis and oxidation is accomplishedusing the bacterial composition according to the present invention. Thiscomposition is particularly effective when the fatty effluent issupplied continuously. This is why biodegradation of fats is effecteddirectly on the untreated effluent, working on the flow.

[0044] The effectiveness of said composition depends on the dilutionrate at the facility. This dilution rate corresponds to the ratiobetween the effluent output and the volume of the biological reactor 3and depends on the fat concentration initially present in the effluentto be pre-treated.

[0045] According to another advantageous characteristic of theinvention, the process according to the present invention ischaracterised in that the rate of dilution obtained in the biologicalreactor 3 is inversely proportional to the fat concentration initiallypresent in the effluent to be pre-treated and is situated preferablybetween 0.528 h⁻¹ and 1.056 h⁻¹ for a concentration of fats contained insaid effluent to be pre-treated entering the homogenisation and/orprocessing vessel 1 of 1 g/l.

[0046] Since the dilution rate is inversely proportional to theconcentration of fats initially present in the effluent to bepre-treated, each of the limit values of the rate ranges indicated above(given for a fat concentration of 1 g/l) need only be divided by theappropriate factor to determine the ranges of dilution rates to be usedfor other concentrations of fats. Thus, for an initial concentration offats of 0.5 g/l, the dilution rate will be between 0.800 h⁻¹ and 3.000h⁻¹, preferably between 1.056 h⁻¹ and 2.112 h⁻¹, while for an initialfats content of, for example, 4 g/l, said dilution rate will be between0.100 h⁻¹ and 0.375 h⁻¹, preferably between 0.132 h⁻¹ and 0.264 h⁻¹,etc.

[0047] Advantageously, the process in accordance with the presentinvention is characterised in that the fat concentration in the effluentto be pre-treated entering the homogenisation and/or processing vessel 1is less than 40 g/l, and preferably situated between 0.5 g/l and 10 g/l.In fact, too low a fat concentration is likely to damage the properdevelopment (growth) or live preservation of the cultures ofmicro-organisms, and therefore the chemical performance and economicprofitability of the process, and similarly too high a fat concentrationmay also inhibit bacterial growth.

[0048] If the supply of fatty effluent to be treated is not continuous,correct degradation of lipids (in other words an output of the order of70 to 99%) is generally achieved in 30 to 40 hours.

[0049] In continuous mode, as previously indicated, the dilution rate offats initially present in the effluent to be pretreated must be between0.400 h⁻¹ and 1.500 h⁻¹ for a concentration of fats contained in saideffluent to be pre-treated entering the homogenisation and/or processingvessel 1 of 1 g/liter. Outside this range of dilution rate values, it ispossible that the lipid degradation activity may reduce significantly.

[0050] According to a variant, the effluent to be pre-treated may alsobe subjected to a prior screening operation 9 with a view to separatingany solid matter present in said effluent, before said effluent reachesthe homogenisation and/or processing vessel 1. This measure allows thesize of solid particles poured into said homogenisation and/orprocessing vessel 1 to be limited, by trapping, for example, solidparticles with sections of more than 1 cm².

[0051] The homogenisation and/or processing vessel 1 is equipped with anagitator or any other means of agitation normally used in theseapplications that permits good mixing and therefore good homogenisationof the effluent (temperature, pH, fat concentration, etc.).Advantageously, the effluent arrives from above into said vessel 1, andthis allows the biomass to be well dispersed. From said homogenisationand/or processing vessel 1, the effluent is pumped at an output thatdepends on the above-mentioned dilution rate and thus the fatconcentration, towards the biological reactor 3. This reactor isequipped with an aeration device and a pump (not illustrated) thatallows the recirculation circuit 2 between said biological reactor 3 andsaid homogenisation and/or processing vessel 1 to be activated.

[0052] In a particularly advantageous variation, illustrated in FIG. 2,the arrival in the homogenisation and/or processing vessel 1 of therecirculation water discharged by the recirculation circuit 2 iseffected from above by a spraying device 4. In this way, the potentialformation of a layer of fat on the surface of said homogenisation and/orprocessing vessel 1 is avoided.

[0053] Biological degradation occurs principally in the biologicalreactor 3 due to oxygen enrichment of the medium, for example by usingan aeration or oxygenation device, preferably using at least one devicefor providing a controlled supply of oxygen 7.

[0054] In fact, the quantity of air to be injected into the biologicalreactor 3 must be sufficiently large for development of the biomass tooccur but must not cause fats to float in said biological reactor 3. Airis introduced preferably by coarse bubbling.

[0055] From the biological reactor 3, the pre-treated effluent overflowsand runs by gravity into a decanter 5 where the particles that can bedecanted form a sediment. According to a preferred embodiment, thepre-treated effluent is discharged by means of a decanter 5 over theupper part of which a floating pump 6 is provided to expel surfacefloating sludge that cannot be decanted.

[0056] The decanter 5 is preferably cone-shaped at the base and thepre-treated water similarly runs off by overflow.

[0057] The following table gives examples of results obtained whenimplementing the process for effluent originating from variousindustrial sectors: Fat from Effluent from Effluent from Effluent fromproduction of a a caterer a pork butcher poultry abattoir animalfeedstuffs UW PTW O UW PTW O UW PTW O UW PTW O g/l g/l % g/l g/l % g/lg/l % g/l g/l % Fat conc. 3.00 0.15 95 2.60 0.10 96 0.65 0.12 82 56.063.18 95 COD 3.73 1.12 70 1.86 1.10 41 4.52 1.64 64 93.30 8.69 91 BOD₅1.14 0.51 55 2.45 0.82 67 TMS 1.38 0.61 56 1.55 0.28 82 1.60 0.54 6676.43 4.96 94

[0058] The average time effluent remains in the facility according tothe invention is of the order of 24 hours.

[0059] To further increase the output of the process, surface floatingsludge that cannot be decanted may be reinjected into, or upstream of,the homogenisation and/or processing vessel 1, for example by means ofthe recycling circuit 8 illustrated diagrammatically in FIG. 1. Theexcess sludge that can be decanted is discharged.

[0060] The present invention also relates to a facility for pre-treatingeffluent rich in organic fats, and is intended particularly, but notrestrictively, for implementation of the pre-treatment process describedabove.

[0061] This facility consists principally, as is shown in FIG. 2 of theaccompanying drawings, of at least one homogenisation and/or processingvessel 1, at least one biological reactor 3 of a capacity suited to thedaily output of effluent to be pre-treated and its fat concentration,said biological reactor 3 being connected to the homogenisation and/orprocessing vessel(s) 1 by a recirculation circuit 2, at least one devicefor providing a controlled supply of oxygen 7 arranged in the biologicalreactor(s) 3 and at least one means of discharging the pre-treatedeffluent, for example by overflow, outside said biological reactor(s) 3.For reasons of clarity, the recirculation circuit 2 has not beenillustrated in FIG. 2.

[0062] Advantageously, the biological reactor 3 is configured tofacilitate extraction of the residual sludge by the decanter 5, and torender it suitable to receive at least one device for providing acontrolled supply of oxygen 7 which, by supplying a large injection ofoxygen, permits maintenance or acceleration of the development andactivity of bacterial biodegradation in order to bring biologicalpollution rapidly to an acceptable level for final treatment, forexample in a purification plant.

[0063] The biological reactor 3 may be arranged inside a storage tank,enclosing the device for providing a controlled supply of oxygen 7, forexample a small bubble diffuser, and may be provided with traditionalmeans of injecting chemical and/or biological products to promotepurification. It is also advantageously equipped with the usual means ofanalysis and quality control of effluent before and/or after treatment,notably of its degree of fat pollution and/or level of oxygenation.These means of analysis and other technical devices (pumps, generators,valves, control panel, etc.) are preferably arranged together in atechnical installation 10.

[0064] Said biological reactor 3 may, for example consist of a reactorof the type manufactured by the applicant. The residual sludge obtainedafter extraction of the liquid effluent comprises firstly, suspendedmatter that can be decanted and is not easily biodegraded and secondly,surface floating sludge that cannot be decanted which can be reinjectedinto or upstream of the homogenisation and/or processing vessel 1 by anappropriate recycling circuit 8.

[0065] Sludge that can be decanted may be discharged, with a view tostoring or spreading it. The final sludge may also, depending on thequantities produced and the capacity of the decanter 5, remain stored insaid decanter 5 for complete extraction and cleaning every 1 to 2 years,for example.

[0066] In order to eliminate large solid particles and limit the amountof matter to be decanted, provision may advantageously be made for theeffluent to be sieved or screened 9, possibly in association withdecanting, before being poured into the homogenisation and/or processingvessel 1. In this case, the necessary equipment, known per se, may beadded to the facility.

[0067] Advantageously, the facility according to the invention iscollected together in an oval vessel 11, preferably, made of concreteand compartmented into three tanks, which may be buried or half-buried,the machinery being collected together in a technical installation 10placed above said oval vessel.

[0068] The facility according to the invention may also comprise atleast one process control and management unit, for example of theprogrammable controller type, which automatically controls the progressof the successive stages of treatment, by being linked to suitablesensors and actuators.

[0069] In the case of effluent from the food industry, for example, froman average pie production unit, the quantities of fats treated may be ofthe order of a tonne of fat per day, which corresponds to 35 m³ per dayof discharge at about 5 g/l of fats.

[0070] Of course, the invention is not limited to the embodimentdescribed and illustrated in the accompanying drawings. Modificationsare possible, particularly from the point of view of the composition ofthe various elements or by substitution of technical equivalents,without however departing from the scope of protection of the invention.

1. Bacterial composition for the degradation of organic fats,characterised in that it comprises principally the bacterial strainKlebsiella oxytoca.
 2. Composition according to claim 1, characterisedin that it comprises in addition the bacterial strain Serratia odoriferaand/or Aeromonas hydrophyla.
 3. Composition according to claim 2,characterised in that it is composed of 60% to 90%, preferably about 80%by weight of bacteria of the strain Klebsiella oxytoca, 5% to 20%,preferably about 10% by weight of bacteria of the strain Serratiaodorifera, and 5% to 20%, preferably about 10% by weight of bacteria ofthe strain Aeromonas hydrophyla, the total of the three strains beingequal to 100%.
 4. Use of a bacterial composition according to any one ofclaims 1 to 3 for the treatment or pre-treatment of effluent rich inorganic fats, particularly effluent from the food or agro-food industry.5. Process for the pre-treatment of effluent rich in organic fats,particularly effluent from the food or agro-food industry, characterisedin that it consists of pre-treating directly said effluent containingsaid fats as it leaves the place of its production and in that itconsists of accomplishing the following stages: supplying ahomogenisation and/or processing vessel (1) with effluent to bepre-treated, as it is produced and activating a recirculation circuit(2) between the vessel and a biological reactor (3) so as to obtain insaid biological reactor (3) a dilution rate of the fats inverselyproportional to the fat concentration initially present in the effluentto be pre-treated and situated between 0.400 h⁻¹ and 1.500 h⁻¹ for a fatconcentration contained in said effluent to be pre-treated entering thehomogenisation and/or processing vessel (1) of 1 g/l, degrading saidfats in said biological reactor (3) using a bacterial compositionaccording to any one of claims 1 to 3, and discharging the pre-treatedeffluent, now containing practically no fats, to a final treatment unitsuch as a purification plant.
 6. Process according to claim 5,characterised in that the dilution rate obtained in the biologicalreactor (3) is inversely proportional to the fat concentration initiallypresent in the effluent to be pre-treated and preferably situatedbetween 0.528 h⁻¹ and 1.056 h⁻¹ for a fat concentration contained insaid effluent to be pre-treated entering the homogenisation and/orprocessing vessel (1) of 1 g/l.
 7. Process according to any one of claim5 or 6, characterised in that the fat concentration of the effluent tobe pre-treated entering the homogenisation and/or processing vessel (1)is less than 40 g/l, and preferably situated between 0.5 g/l and 10 g/l.8. Process according to any one of claims 5 to 7, characterised in thatthe arrival in the homogenisation and/or processing vessel (1) of therecirculation water discharged by the recirculation circuit (2) iseffected from above by a spraying device (4).
 9. Process according toany one of claims 5 to 8 characterised in that the pre-treated effluentis discharged using a decanter (5) on the upper part of which a floatingpump (6) is provided for the elimination of surface floating sludge thatcannot be decanted.
 10. Process according to claim 9, characterised inthat the surface floating sludge that cannot be decanted is reinjectedinto, or upstream of the homogenisation and/or processing vessel (1).11. Facility for the pre-treatment of effluent rich in organic fats, inparticular for the implementation of the process according to any one ofclaims 5 to 10, characterised in that it consists principally of atleast one homogenisation and/or processing vessel (1), at least onebiological reactor (3) of a capacity suited to the daily output ofeffluent to be pre-treated and to the fat concentration of thateffluent, said biological reactor (3) being connected to thehomogenisation and/or processing vessel(s) (1) by a recirculationcircuit (2), at least one device for providing a controlled supply ofoxygen (7) arranged in the biological reactor(s) (3) and at least onemeans of discharging the pre-treated effluent, for example by overflow,outside said biological reactor(s) (3).